In brief
- A roof that holds water after Gu or Deyr rain is carrying extra load and testing every joint at once.
- A fall set by eye, or a drain fixed above the surrounding surface, leaves water standing and shows up as ponding, blistered membrane and cracked parapets.
- The fix is a water test and recorded levels before the membrane goes down, plus a drain check after every rain.
Contents
A roof that holds water after rain is carrying extra load and testing every joint at once. The water finds any low spot, softens the joint and adds weight exactly where the structure is weakest. That is how roof falls skills gaps in Bosaso can turn into standing water: a crew can lay membrane neatly and still leave water sitting against a parapet or around a drain. The defect stays invisible on a dry day.
What do poor roof falls look like on site?
Ponding is the visible symptom: water sits more than a day after rain instead of running to a drain. It happens when the slope is set by eye, when the screed is laid without a level or laser, or when the drain outlet is fixed higher than the surrounding surface. A second site symptom is membrane work: laps laid the wrong way, or a membrane run up a parapet without a proper upturn and termination. A third is detail work at rain water outlets, pipe penetrations and upstands, where the crew has to shape the material rather than roll it out flat. None of this is a knowledge problem in the abstract. It is a practice problem: the person holding the level, the trowel or the welding torch has not done enough of this work under someone who checks it. Ask any roofing crew how they set a fall before screeding, with a string line, a laser level or a pre-formed slope, and ask to see where they have done it.
How does standing water turn into a roof problem?
Standing water loads the slab, and it keeps loading it until it dries or is drained. The load concentrates at the low point, which is usually the same place the membrane is stressed. Cycles of wetting and drying open laps, grow algae and plant roots in silt at the drain, and corrode any embedded steel at a crack. Once water reaches the slab through a failed termination, the reinforcement can start to corrode and expand, and that cracking shows on the underside as a stain or a line. The roof does not fail in one event. It fails in stages, and each stage is easier to spot early than to repair. Confirm the design loads and drainage requirements with the engineer who signed the drawings, and ask them to check the intended fall against the drainage layout before work starts.
How do you check the work before it is covered?
Ask for a water test before the final surface goes down: pond the roof, or flood it in sections, and mark where water still sits after a set period agreed with the engineer. Where the site is exposed to salt spray, check fixings, flashings and any metal edge for corrosion and correct fixing. Set test points with a straight edge and a spirit level at the drain, at the parapet and at the mid-span, and record the readings. Photograph the drain before screeding and after, so a later blockage can be traced to construction debris or to use. Ask the contractor for their method statement and any test records for this project. Ask the municipal engineer's office what drainage and permit requirements apply to the plot, and whether it holds records for the building. Keep the water test record with the as-built drawings.
What to do next
Before the membrane or final screed goes down, arrange a water test with the roofing contractor and your engineer. Agree in writing how long water will stand, who reads the levels, and what counts as a fail. Photograph the drains and the test, then keep those records with the drawings.
Frequently asked questions
How long should water stand on a roof during a test in Bosaso?
The period is set by the project specification, so agree it with the engineer before the test rather than using a number from a website. After the agreed time, no water should remain ponded away from the drain.
Can a roof fall be corrected after the membrane is laid?
Correcting the slope usually means removing the covering, re-screeding and re-laying the membrane, which costs far more than getting the fall right first. If water already ponds, ask the engineer to assess whether the drain can be lowered or a local repair made before stripping the whole roof.
Local reporting: this article is written for building work in Bosaso and Puntland. Ground conditions, prices and rules differ between places; confirm the details for your own site.